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The Western HVDC Link

Alan Capon
I did originally answer the previous thread, but have since deleted my response and I believe a new thread with a proper and correct title is the correct way of answering. 


More info on the fault here: https://www.energy-reporters.com/transmission/italys-prysmian-under-fire-over-uk-interconnector-failure/ 


Reports suggest an undersea cable fault in the vicinity of Liverpool Bay. 


Regards,


Alan.
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    No such thing as a silly question! With a long transmission line, you get a phase shift along its length due to its reactance. This exact phase shift is a function of distance, as well as load. If youHave a second cable of a different length, it is likely that the difference in phase (even though the frequency is the same) will prevent you from being able to close the second end. The solution is a dc link, with the “inverter” in synchronism with the local grid connection point. 



    Thanks Alan - I did wonder if it might be something along the lines of 'propagation delay' over such a long length, but figured that it must be a similar length to the existing England - Scotland lines of the grid so any delay would be similar for both and so everything should 'come out in the wash' as it were. Perhaps undersea cables have a different reactance (per m) from overhead lines and that makes a difference?

       - Andy.
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  • 0

    No such thing as a silly question! With a long transmission line, you get a phase shift along its length due to its reactance. This exact phase shift is a function of distance, as well as load. If youHave a second cable of a different length, it is likely that the difference in phase (even though the frequency is the same) will prevent you from being able to close the second end. The solution is a dc link, with the “inverter” in synchronism with the local grid connection point. 



    Thanks Alan - I did wonder if it might be something along the lines of 'propagation delay' over such a long length, but figured that it must be a similar length to the existing England - Scotland lines of the grid so any delay would be similar for both and so everything should 'come out in the wash' as it were. Perhaps undersea cables have a different reactance (per m) from overhead lines and that makes a difference?

       - Andy.
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